Sofa bed mechanisms typically include three sections, namely, a head section, an intermediate section and a foot section. The sections may be extended horizontally to a bed position or folded and stored in a sofa position. Ordinarily, to move the mechanism to the sofa position, the foot section is folded onto the intermediate section and the mechanism is pushed into the furniture which houses the mechanism. The sections also support a mattress, and the head and intermediate sections normally carry a spring or fabric deck which in the sofa position is relatively limp. Thus there is no firm support for the sofa cushion or cushions.
Although these conventional sofa beds have in general been satisfactory, their substantial sizes have dictated that the furniture in which the mechanism is embodied be large in width, that is, large in a direction front of rear of the furniture. This severely limits the types of furniture which may be used. U.S. application Ser. No. 127,919 filed Mar. 6, 1980 and assigned to the assignee of this invention, discloses a compact sofa bed mechanism which is of a shallow dimension in a direction front to rear of the sofa. The foot section is folded onto the intermediate section, which in turn is folded onto the head section so that in the sofa position the foot section is sandwiched between the head and intermediate sections. The sofa bed disclosed therein has been advantageous from the standpoint of width and has proved excellent in operation. However, it lacks a protective deck member, since in the sofa position the intermediate section is on the top of the stack and it is usually unfeasible from a strength standpoint to provide the intermediate section with a fabric grid rather than a spring grid. Even if the intermediate section is provided with a fabric grid, this grid is usually deficient as a deck member in the sofa position, since it will present a loose and discontinuous surface to the sofa cushion or cushions. It is an object of the present invention, therefore, to provide an overdeck assembly adapted to overlie the stacked sections in the sofa position and which forms a taut and continuous support surface for the sofa cushions.
Another disadvantage to conventional sofa beds and to the type disclosed in the aforementioned application is that they are subject to the problem of side-to-side sway in the sofa position. This is, the weight of a user sitting at one side of the sofa can cause the sides of the mechanism to move independently of each other and thus cause the sofa to sink under the user. The provision of cross tubes can solve this problem, but such cross tubes normally interfere with sleeper comfort in the bed position. It is another object of this invention, therefore, to provide an overdeck assembly which provides resistance to side-to-side sway while remaining free from interference with sleeper comfort.